1. Field of the Invention
The present invention relates to an optical pickup apparatus.
2. Description of the Related Art
Since an optical recording medium can record a high capacity data signal in high density, it is widely applied in fields requiring recording and reproduction of data.
Recently, as data such as a moving image requiring a high capacity recording medium increases, a study is in progress to manufacture a high capacity optical recording medium through reduction of a recording pit and a track pitch.
Generally, it is desirable to accurately track a light beam on a track of an optical recording medium in order to reproduce a data signal recorded by a micron unit.
Various methods are known as a method for detecting a tracking error signal (TES) for accurate tracking. A push-pull method is known as one of the simplest methods.
However, according to the push-pull method, an offset is generated to a TES when an objective lens is shifted in a radial direction or when a disk is inclined. Therefore, a differential push pull (DPP) method using three beams has been developed to remove this offset.
However, since two sub-beams need to be separated by ½ track pitch with respect to a main beam in the DPP method, it cannot be applied to an optical recording medium having a different track pitch.
For example, since either 0.74 μm or 1.23 μm can be used as a track pitch of an optical recording medium, an optical pickup apparatus that can record and reproduce a predetermined optical recording medium such as the recording medium having the 0.74 μm track pitch cannot record and reproduce another optical recording medium such as the recording medium having the 1.23 μm track pitch.